The ear transfers sound through the external ear canal and middle ear into the inner ear (cochlea). The external ear canal collects sound pressure waves and transfers them to the tympanic membrane. The middle ear, which includes tympanic membrane (or eardrum) and three ossicular bones (i.e., malleus, incus and stapes) suspended in an air-filled cavity (i.e., middle ear cavity) by suspensory ligaments/muscles, is an extremely small structure with complex shape. Sound collected in the ear canal entry and passed to the middle ear through the tympanic membrane (TM) initiates the acoustic-mechanical transmission in the ear. The middle ear builds a mechanism (ossicular chain) for transmitting vibrations of the TM to the fluid in cochlea. A number of parameters such as the shape and stiffness of the TM, shape and volume of the external ear canal, and volume and pressure of the middle ear cavity directly affect acoustic-mechanical transmission through the ear. Changes of these parameters are often related to patho-physiological conditions in the ear.
Since the transfer function of the middle ear cannot be measured readily in living humans, various different theoretical modeling methods have been developed to simulate the functions of the ear. Among them, analogy-modeling method (represented by circuit or lumped parameter models) proved to be an important tool and was widely employed in the ear mechanics32, 31, 33, 17, 10, 34. Other quantitative middle ear models, including analytical model23 and multibody model12 also presented valuable findings in predicting normal and pathological mechanics of the middle ear. Early modeling of middle ear function used a transformer analogy with circuit models or lumped parameter models reported by Zwislocki31, Kringlebotn17, and Hudde & Weistenhöfer12.
While the analytical approach worked reasonably well for some limited situations, it was not always possible to model the realistic acoustic-mechanical response in the ear involving complex geometry and an array of material compositions. The finite element (FE) method, a general numerical procedure, has distinct advantages over analytical approaches in modeling complex biological systems. The FE method is always capable of modeling the complex geometry, ultrastructural characteristics, and non-homogenous and anisotropic material properties of biological systems. FE models can also determine the detailed vibration shapes, stress distributions, and dynamic behaviors at any locations in a system, which is not possible with analytical solutions. The first FE model of the ear (for cat eardrum) was reported by Funnell and Laszlo in 1978.5 In 1992, a three-dimensional (3-D) FE model of middle ear was published by Wada and Metoki28 to investigate vibration patterns of the middle ear system. Since then, FE modeling of the static and dynamic behaviors of the middle ear subsets or entire middle ear has become a rapidly growing research area in ear mechanics.15,13,17 A thorough literature survey about the FE modeling of ear mechanics was summarized in a previous publication.26 
Using the combined technologies of FE analysis and 3-D reconstruction of human middle ear, a geometric (computer-aided design (CAD)) model and FE model of the middle ear was constructed based on a set of digitized section images of one human temporal bone (right ear, age 52, female).7,25,26 To date, this FE model may represent the best geometric configurations of the middle ear ossicles and eardrum and has the capability for analysis on transmission of sound pressure-induced vibrations through the middle ear. However, this FE model needs further improvements to include the external ear canal, middle ear cavity, and cochlea in order to simulate the complete acoustic-mechanical transmission in the ear. The individual variation of temporal bones in geometry and material properties also needs to be identified through models constructed from different temporal bones.
Using the combined technologies of FE analysis and 3D reconstruction of the middle ear, the first FE model of human middle ear with the TM, ossicular bones, middle ear ligaments/muscle tendons, and middle ear boundaries7, 25, 26 was developed. However, the ear is a complex system formed of air, liquid and mechanical structures making the function of the ear a very difficult system to understand and simulate. Thus, there remained a need to accurately model the interactions between the various anatomical structures of the ear including the acoustic-mechanical transmission through the ear. It is to such an improved model of the ear that the present invention is directed.